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Scientists study oil seepage to learn more about climate

Molly Peterson|January 29, 2009

The state lands commission considers today whether to allow an oil company to drill new wells from an existing platform off the Central Coast. California oil-seekers have long chased tar balls and oil slicks to determine where to drill. Now, scientists are using seabed seeps of oil and gas to learn more about climate. KPCC's Molly Peterson talked with some UC scientists who study seeps in Santa Barbara.

Molly Peterson: Santa Barbara seeps spit out a hundred barrels of oil a day. That's no surprise to surfers who've stepped in tar balls. Ten years ago, UCSB marine geophysicist Bruce Luyendyk monitored seeps near Platform Holly, on Coal Oil Point. He and other scientists figured that seeps spat out less oil and half as much gas during years that oil companies drilled nearby.

Bruce Luyendyk: So we came up with this hypothesis that increased draw down of the oil reservoir was causing drops in pressure in the subsurface and the pressure was driving the seepages. Therefore that seemed like a reasonable story. So that's pretty much where we left it.

Peterson: Until last year. Activists and politicians seized upon his work to support their arguments for more drilling. Luyendyk objected.

Luyendyk: The notion that we would create a broad sweeping strategy based on a study done here, which although it's robust, still remains a hypothesis, is misguided.

Peterson: Luyendyk says chronic oil seeps are different from a catastrophic spill like the one 40 years ago. But seeps contribute more than half the oil content in the world's oceans – and plenty of gas in the atmosphere. So Luyendyk and other UC Santa Barbara researchers want to understand how those seeps behave.

Luyendyk: We want to see where these things pop up, where they disappear, what's the frequency, or the causes of their events like changes in ocean temperatures that affect it. You can think of any number of different variables.

Peterson: Much of their work now focuses on measuring gas from the seeps.

Peterson: It's a glassy-water day off Coal Oil Point in Santa Barbara, but waters right around us are fizzing like soda. [Sound of bubbles] They push the boat around at Shane Seep, making anchoring tricky for the captain. His name's Shane Anderson – the site's named for him.

Anderson: So the plume mushrooms out at the surface, pushes the boat off. It's hard to stay right there.

Peterson: Bubbles rise from the seabed – the gas inside them originates in a reservoir 1,500 meters below that. The UC Santa Barbara boats are trying to measure the gas bubbles carry.

[Sound of diver readying his regulator]

Peterson: Anderson and grad student Chris Stubbs will dive to the seep.

Chris Stubbs: We're taking down that piece of apparatus over there, it's called a Bubble Measurement System.

Peterson: It's a metal frame, and strapped to it is a camera pointed at a plastic screen, with lights. Round yellow buoys keep it upright. The camera will record plumes of bubbles passing to the surface.

Ira Leifer: We'll go to the main vent, we'll put the system down at the sea bed. When we're ready, two lights on.

Peterson: Cameras, sonar, and sampling have helped estimate seep gas so far. UC Santa Barbara researcher Ira Leifer says now his team's trying something new: listening to seeps with a hydrophone – a microphone that can get wet.

Leifer: The sound or music of the bubbles would relate to the flux – so how many bubbles are coming out per second – we're collecting sound of the bubbles to demonstrate that this was the case.

[Splash of diver heading overboard]

Peterson: They're listening for methane – a greenhouse gas many times more effective at trapping heat than carbon dioxide.

Leifer: Globally seeps are estimated to contribute 7 to 10 percent of the natural methane budget.

Peterson: And Coal Oil Point is a big source of methane in the sea. Observing methane moving from the seabed up to the surface, Leifer believes, can tell scientists more about its possible warming effects around the world.

Leifer: And we can put this in a model and then figure out how much methane gets to the atmosphere.

Peterson: The divers return to the surface a little disappointed. Anderson says it was hard to see well enough to measure the bubbles.

Anderson: It's very silty. And then the bubbles are coming up all by you so you can see them. And then the lights, when the lights come on it reflects on the particulates and glows all around us. So it's pretty hard to tell what's going on.

Peterson: Leifer would like to monitor seeps better around the globe. Doing that with sound could be relatively cheap. But he says it's still hard to predict how much gas will emerge from just one seep field in Santa Barbara.

Leifer: I mean, I have measurements of a vent, for a few seconds. There's no reason to believe that that particular vent, few seconds later, is doing same thing.

Peterson: It'll take more trips like this one to understand the music of the seeps. Right now, Leifer and the other UC Santa Barbara scientists are still learning the tune.